Besides some Martian meteorites collected on Earth, some gravity data from spacecraft and other bits of information, our knowledge of the planet's insides is small, said Bruce Banerdt, the principal investigator of a new lander called InSight, at NASA's Jet Propulsion Laboratory in California. But that's about to change.

InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) will launch for Mars in March on a quick six-month journey to the Red Planet. Upon arriving at the Martian equator, the spacecraft will deploy a small drill to probe the planet's interior and a seismometer to measure any "marsquakes" that occur.

"Mars is a really good laboratory to understand how planets form into the complex bodies they are," Banerdt told Discovery News. This is because the lack of plate tectonics means the planet did not meld its early rocks into the interior (unlike Earth). Also, it's big enough to have a complex interior with a core and mantle, unlike Earth's nearby moon.

For the past two months, engineers have been testing InSight's chops at a Lockheed Martin facility in Colorado. So far, things are going well, the company says. The contractor has decades of experience working with NASA and helps to operate two spacecraft that will relay information from InSight to orbit - Mars Odyssey and Mars Reconnaissance Orbiter - and then to Earth. (MRO was recently repositioned in orbit to help with InSight's landing.)

Testing is divided into two phases - the launch and cruise to Mars, and then the complex entry, descent and landing. Luckily for InSight, a similar system was tested before when the Phoenix lander safely made it to the surface in August 2007. But there still are a number of steps to consider, including separating the lander from the cruise shield and safely deploying the legs InSight will rest on while sitting on the surface.

"After we touch down, the first most critical event is the deployment of the landing solar array," Stu Spath, InSight program manager at Lockheed Martin Space Systems Co., told Discovery News. "It will unfurl into a nearly circular pattern and collect the solar energy for power. Then we'll test our most critical components and do a communications check to communicate properly (to Earth)."

The first 80 sols (Martian days) of work will be busy. In the first 40 sols, InSight will test out its systems and place the seismometer on the surface. Then comes the drill. It will be slowly lowered below the surface a half-meter (1.6 feet) at a time. Investigators will then take a few days to send out a heat pulse to see how the environment around the drill is reacting. The mission goal is to get the drill at least 3 to 5 meters (10 to 16 feet) deep.

The Apollo astronauts famously struggled to get small drill samples in and out of the moon's interior because the dust was so densely packed, but the InSight team does not expect a similar situation on Mars. Wind and other processes mixed up the dust inside so it's not as uniform as on the moon, Banerdt said, and there are some measurements of dust cohesiveness at similar sites that the Spirit and Curiosity rovers explored. Scientists also have done numerous drill tests with analog soils at JPL and other facilities.

InSight will land in the Martian fall and is expected to last for at least one Martian year - roughly two years on Earth. Enhanced insulation and a large solar panel are supposed to keep the spacecraft warm, happy and functioning through winter. And unlike a rover, the spacecraft just has to sit there and collect data - less power required.

The hope is, Banerdt said, to capture 20 to 100 marsquakes over that Martian year to learn more about the planet's interior and map where any interior boundaries are. The mission may be able to last longer if the components hold out and the funding is available, he added.

Scientists are meeting this week to discuss landing sites for NASA’s next Mars rover, an ambitious mission that not only will attempt to look for past life on Mars, but also stash samples drilled out from rocks for a future rover to retrieve and fly back to Earth for analysis. The point of the meeting is to discuss the current top candidate landing sites, though the list likely will change as new images and science data come in from satellites orbiting Mars and from NASA’s ongoing Curiosity and Opportunity rover missions.

The new mission, still generically referred to as Mars 2020, is due to blast off in July or August 2020 and land itself in February 2021 using a heat shield, parachutes and Curiosity’s “skycrane” tethered descent system (pictured here). Engineers also are working to develop a “terrain recognition navigation” system that would allow the descending spacecraft to take pictures and match them with imagery stored in its computer for more precise steering. That system could make many more potential landing sites safe for touchdown. Another concern is how fast the rover could traverse the surface so that it can meet its mission goals, including drilling and cache 20 samples, in one Martian year, or 668 Earth days.)

Tucked between a large volcano and an ancient impact basin is a region known as Nili Fossae, which is marked by wide, curved troughs cutting about 1,600 feet into the Martian crust. Nili Fossae is replete with clay-rich rocks, which form in the presence of water and which may be key to finding preserved organics. Nili Fossae was a top candidate for NASA’s ongoing Curiosity mission, but the site was cut due to engineering concerns.

Scientists believe water once flowed and pooled inside an ancient crater known as Jezero, located near the Martian equator. The water streamed in from the northern and western sides of the crater, now marked by dried out channels, and eventually overflowed the crater’s southern wall, creating a third channel. Scientists do not know how long the water existed, though they do think there were at least two separate water events before the area dried out between 3.5 billion and 3.8 billion years ago. Chemical data collected by Mars orbiters show Jezero has clay and carbonate minerals that were altered by water. If life evolved during the time when Jezero was flush with water, it may be preserved in the sediments.

Ancient exposed bedrock and a diverse collection of hydratated minerals got this site a spot on the Mars 2020 candidate landing list. The targeted zone is located in the northeast part of Syrtis Major, a huge shield volcano and near the northwest rim of the giant impact basin Isidis Planitia.

Scientists took a long, hard look at 100-mile wide Holden Crater before deciding to send the Curiosity rover to Gale Crater instead for a mission to assess if Mars ever had all the ingredients necessary for life. That goal was met less than seven months after the rover’s Aug. 3, 2012, touchdown.
Holden, along with Eberswalde Crater and Mawrth Vallis, made to the short list of Curiosity candidate landing sites and remains of interest to scientists on the follow-on Mars 2020 mission to actually look for signs of ancient life and cache samples for an eventual return to Earth.

Holden Crater was once believed to have been “Holden Lake.” It contains two layers of sediments, the lower of which is believed to have formed in a large lake. The upper layer likely formed when water pooled in an area to the south known as Uzboi Vallis broke through Holdin’s rim. The current must have been strong, capable of transporting boulders dozens of feet in diameter. Within Holden’s ancient basin are numerous smaller craters, many of which are filled with sediments.

The widest segment of the massive Valles Marineris canyon system is known as Melas Chasma, which cuts through layered deposits believed to be sediments from an ancient lake. Melas has hydrated sulfates and other minerals transformed by water. The southwest region contains fan-shaped structures, indicating the lake’s water level fluctuated. Another attraction is the site’s proximity to seasonal features, known as recurring slope linea, or RSL, which may be signs of present day briny water near the surface, which potentially could be explored during a mission extension.